1. Field of the Invention
The present invention relates to a rail mounting device for fitting a rail into an electrical equipment of relatively small type such as an electromagnetic contactor.
FIG. 7 is a front view of a conventional rail mounting device thereby an electrical equipment is mounted on a rail. In FIG. 7, reference numeral 1 designates a case of the electrical equipment, and 2 designates a recess formed in a bottom surface of the case 1 into which a rail 40 is fitted. A holding claw 3a is formed on one of the side walls of the recess 2. In mounting the case 1 on the rail 40, one edge 41b of the rail 40 is first brought into engagement with the holding claw 3a so as the rail 40 to be fitted into the recess 2 and then the other edge 41a thereof is firmly supported by a tip end of a movable claw 30 provided to the case 1.
FIG. 8A is a magnified bottom view of a portion A including the movable claw 30 in FIG. 7, together with the part of the case 1 and recess 2. 21 denotes a sliding groove provided in the bottom surface of the case 1, which is intersecting at right angles with the recess 2. On the bottom surface of the sliding groove 21, there are formed with a pair of receiving shelves 22 facing the recess 2 side so that the opening portion of the sliding groove 21 is gradually expanded in two steps from the recess 2 side toward the opposite side thereof. 23 is a spring receiver protrudedly formed on the bottom surface of the sliding groove 21. The movable claw 30 is formed by molding synthetic resin, and is slidably inserted into the sliding groove 21.
A longitudinal central portion of the movable claw 30 is formed thick and has a width slightly narrower than the interval between the pair of receiving shelves 22. A rail fitting portion 31 is provided on the tip end of the movable claw 30. Sliding guide portions 32 having a thickness fittable into the sliding groove 21 are formed at both sides of central thick portion of the movable claw 30, and stoppers 33 are formed at the rear end thereof. The movable claw 30 has a window hole 34 with a spring seat 35 formed at the front end thereof. Reference numeral 36 designates a coil spring.
For attaching the movable claw 30 to the case 1, the movable claw 30 is inserted into the sliding groove 21 from the side opposite to the recess 2, and at the same time the coil spring 36 is mounted between the spring receiver 23 and the spring seat 35. As a result, the movable claw 30 moves forward in the sliding groove 21 urged by the coil spring 36, and stops when the stoppers 33 abut against a side surface of the case 1. At this time, the rail fitting portion 31 protrudes into the recess 2 as shown in FIG. 8C to hold the rail 40.
In removing the case 1 from the rail 40, when the movable claw 30 is pulled in a direction opposite to the recess 2, the rail fitting portion 31 is disengaged from the edge portion 41a of the rail 40, and thus, it is possible to readily remove the case 1 from the rail 40. In order to prevent the movable claw 30 from slipping out of the receiving shelves 22 when the movable claw 30 is pulled, the coil spring 36 prevents further movement thereof.
Furthermore, other conventional rail mounting devices of this type are disclosed in Japanese Utility Model Laid-Open Publication Nos. 62-55830 and 62-188035. The electrical equipment with a rail mounting mechanism disclosed in Japanese Utility Model Laid-Open Publication No. 62-55830 includes, as shown in FIG. 9, an electrical equipment main body 37 comprising a recess 38 formed in a bottom surface thereof having respective pairs of first and second holding portions (39, 40) protruding from both sides of the recess towards the center portion thereof for holding a rail 41 to be fitted thereinto, and a holding piece 42 having resiliency and an L-shaped cross section mounted on a stepped portion 43 formed in the bottom to side surfaces of the main body 37, the base portion 44 of the holding piece 42 being joined to the side surface of the electrical equipment main body, while the opposite tip end 45 thereof having a U-shape.
For mounting the electrical equipment on a rail by use of this mounting mechanism, first fit the second pair of holding portions 40 and the tip end 45 of the holding piece 42 to a leg portion 47 of the rail 41, and then the electrical equipment main body 37 is urged by the rail in the direction of the holding piece 42 to turn the holding piece slightly about the base portion 43 thereof. Then, after the other leg portion 47 of the rail 41 has been engaged with the first holding portions 39, the holding piece 42 is returned to its original position by its own resiliency, and the rail 41 is attached by fitting the U-shaped portion 45 of the holding piece to the leg portion 47 of the rail 41.
On the other hand, the rail mounting device for an electrical appliance disclosed in Japanese Utility Model Laid-Open Publication No. 62-188035 includes a case 48 made of synthetic resin and a movable claw 49. The case comprises a stationary claw 50 provided on a first side wall 51 of a bottom recess 52 and engageable with one side edge of a rail (not shown), a guide notch 53 formed in the second side wall 54 facing to the first wall 51 of the bottom recess 52, a holding dent portion 55 formed in a bottom surface of the bottom recess 52 near the second side wall 54 in parallel with the side walls and having a width wider than the guide notch 53, and a holding projection 56 for holding the movable claw 49, which is provided on an outer wall of the case at the near side of the guide notch 53. The movable claw 49 comprises a tongue 57b engageable with the holding projection 56, an engaging arm 57a to be engaged with the holding dent 55 and inserted into the guide notch 53 in such a manner as to move forward and backward, and a holding claw 49 engageable with the other edge of the rail.
In mounting the case on the rail, the tongue 57a of the movable claw 49 is inserted into a square hole 58 of the holding projection 56, and a resilient piece 57 is bent along a slant surface 59 of the guide notch 53 and pushed upwardly to fit the engaging arm 57b into the holding dent portion 55. Then, the stationary claw 50 of the case is brought into engagement with one side edge of the rail, and the movable claw 49 is pushed towards the other side edge of the rail while turning the case 48 about the engaging point so that the case is mounted on the rail.
In the conventional mounting device shown in FIGS. 7 and 8A to 8C, the assembling operation is troublesome, many man-hours are required, and the cost is high because of the adoption of the movable claw 30 and coil spring 36. Furthermore, various problems have been involved in that the case 1 supports the movable claw 30 in the vertical direction only by the slant portions of the receiving shelves 22 as shown in FIG. 8C, whereby the space and length of the slant portions are insufficient for supporting the movable claw 30, and thus the claw 30 is apt to be removed. Moreover, since the slide guide portion 32 is made sufficiently thin so as to be inserted into the slide groove 21, and since the receiving shelves 22 are also made thin in order to keep the product small in size, these parts are tend to be broken easily. In addition, since the slipping off of the movable claw 30 is prevented by utilizing the compression of the coil spring 36, there is difficulty in construction thereof, and the prevention of the slipping phenomenon can not be secured.
In the device disclosed in Japanese Utility Model Laid-Open Publication No. 62-55830, a problem is involved in that since the first and second holding portions are protruded at both sides of the recess, it is not clear how the rail having a width wider than the width between both the holding portions is fitted into the recess to be held thereby. Further, even though the electrical equipments were mounted on the rail, since there is a large play between the rail and the side walls of the recess, it would be difficult to securely mount the electrical equipment on the rail, and the equipment would tend to be out of place due to vibrations, impulses and so on.
Furthermore, in the device disclosed in Japanese Utility Model Laid-Open Publication No. 62-188035, there is a problem in that since the guide notch and the dent portion are formed in the side surface of the case, the structure becomes complicated. Moreover, since a screw driver or the like has to be inserted obliquely to reach the movable claw, a large square window is necessary, and thus the mechanical strength becomes weak and the handling is inconvenient. Furthermore since no measure is provided to prevent the movable claw from slipping out of place towards the rail when the movable claw is accommodated in the case, it tends to be removed in a state that the electrical equipment is not mounted on the rail. In addition, since the sliding movement of the movable claw in the holding dent portion of the case is performed with a cut-out surface of the engaging arm of the movable claw, the movable claw is apt to be stuck in the midway of the sliding movement. Further, since the sectional area of the engaging arm of the movable claw is small, the mechanical strength is weak and tends to be deformed.